US2845710A - Devices for directly measuring and instantaneously recording the angular displacements of a body - Google Patents

Description

Aug. 5, 1958 R. CLARET ETAL 2,845,710 DEVICES FOR DIRECTLY MEASURING AND INSTANTANEOUSLY RECORDING THE ANGULAR DISPLACEMENTS OF A BODY 7 Sheets- Sheet 1 Filed Feb. 17, 1950 Fig.1

Filed Feb. 17,- 1950 Aug. 5, 1958 IIRYCLARET ETAL' 2,845,710

DEVICES FOR DIRECTLY MEASURING AND INSTANTANEOUSLY RECORDING THE ANGULAR DISPLACEMENTS OF A BODY Y 7 Sheets-SheetZ R. cLAR|-:'r ETAL 2,845,710 DEVICES FOR,DIRECTLY MEASURING AND INSTANTANEOUSLY v w w RECORDING THE ANGULAR DISPLACEMENTS OF A BODY Filed F b. 1'7. 1950 7 Sheets-She et s 1958 .CLARET- ETAL 2,845,710 v DEVICES FOR DIRECTLY MEASURING AND INSTANTANEOUSLY RECORDING THE ANGULAR DISPLACEMENTS OF A BODY Filed Feb. 17, 1950 I v 7 Sheets-She s: '4"

. 1958 R ICLARET ETAL 2,845,710

DEVICES F OR DIRECTLY MEASURING AND INSTANTANEOUSLY RECORDING THE ANGULAR DISPLACEMENTS OF A-BODY Filed Feb. 17. 1950 j 7 Sheets-Sheet 5 Aug.- 5, 1958 R. CLARET ETAL 2,845,

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DEVICES FOR DIRECTLY MEASURING AND INSTANTANEOUSLY RECORDING THE ANGULAR DISPLACEMENTS OF A BODY Filed Feb. 17, 1950 7 Sheets-Sheet '7 "Ill J I m. min.

Fig. 9 is a block wiring diagram of the circuit using the output signals of the photo-electric cells.

Figs. 9a through 92 are detailed circuit diagrams showing simple form the basic components of the circuit arrangement of Fig. 9.

Fig. 10 shows three embodiments of the graduations of a limb, in the case of the electro-magnefic reading.

Fig. 11 shows an illustrative embodiment of an electromagnetic reading device.

Fig. 12 shows another embodiment of an electromagnetic reading device.

Fig. 13 is a set of curves showing the electric outputs of the bridge, rectifier and filter, respectively.

Fig. 14 shows an electro-magnetic reading device ensuring in the same time the transmission of the corresponding signals, said device comprising, inter alia, a Wheatstone bridge circuit.

In Fig. 1, the solid body of which it is desired to measure the angular displacements about a fixed point is shown at S. In the selected system, the three rotation axes of the solid S are XX, Y-Y and ZZ, respectively. The angular displacements about axes XX, YY and Z-Z are materialized by three graduated limbs, L L L respectively. The rotation of limb L around axis XX is ensured by a fourth, non-graduated limb l rotatively mounted at both ends of its diameter, which is normal to the plane containing L on bearings 1 and 2. The planes of the graduated limbs L and L are perpendicular to one another as well as their respective rotation axes, one of which, along ZZ, is materialized by a diametral rod 3 extending within the graduated limb L the other rotation axis, along Y--Y, being materialized by two pivots 4, 4 located outside the graduated limb L,. The planes of the graduated limbs L and L are perpendicular to one another as well as their respective rotation axes. Moreover, the three axes converge towards one point 0. Rod 3 carries the reference solid S. The limb L is graduated innerly, while limbs L L are graduated externally. Three microscopes M M and M ensure the optical reading of the respective displacement angles of the reference body on the three graduated limbs L L and L respectively. Said microscopes are continuously maintained in the planes of the corresponding limbs. For this purpose, microscope M may be fixedly secured on plane P (see Fig. 2), microscope M being mounted on the reference body and microscope M being mounted on the axis of bearing 2 and rotating therewith.

In Fig. 2, the origins and directions of angles x, y, and 2 which measure the displacements of solid S about the fixed point 0 around the three axes XX, YY and Z--Z, respectively, are shown in the following manner: the dihedral angle x defining plane P which contains axis ZZ is measured from plane P normal to plane P, the intersection of both last said planes being axis XX and the angles being positive in one direction and negative in the other one.

Angle y defining axis ZZ is measured in each plane P corresponding to angle x from the perpendicular to axis XX, the angles being positive in one direction and negative in the other one.

Angle z defining the position of solid S around axis ZZ is measured in the plane passing through the fixed point 0 and right-angled (-0 axis Z--Z, from the trace, oriented in said plane, of plane P the angles being positive in one direction and negative in the other one.

In Fig. 3, there is shown at 5 the objective of the microscope, at 6 the prism of the vertical illuminator, at 7 the lens system, at 8 the light-tight chamber, at 9 the separating slots constituted by a 60 total reflection prism as shown in detail in Fig. 5, at 1010 the counting and selecting cells, at 11 a re-setting cell, at 12 the cross-section of the cylindrical limb, at 13 the illuminating condenser, at 14 the lamp thereof and at 15 the graduation of the cylindrical limb. The path of the light rays is as follows: lamp 14, condenser 13, prism 6, objective 5,

graduated limb on which the rays are reflected, objective 5, lens system 7, light-tight chamber 8, separating slots 9, cells 1010. As shown in this figure (also in Fig. 4) the microscope has a. magnifying power greater than unity and thus projects on the eye-piece 7 an enlarged image of the graduations.

In Fig. 4, the mode of illumination shown, acts by transparency. In this figure, the parts corresponding to those of Fig. 3 are indicated by the same references. The illuminating means in this embodiment comprises lamp 14 and separate lens combination 13' for concentrating the light on a transparent circular limb 12'. The path of the light rays is as follows: lamp 14, lens combination 13, circular graduated limb 12' through which they are transmitted, objective 5, after which the rays follow the same path as in Fig. 3.

In the case of Fig. 3, the limb graduations 15 are provided on cylinder 12, while in the case of Fig. 4, said graduations are radial and provided on disc 12.

In Fig. 6 is shown on a larger scale the image plan of the photographic chamber with a portion of the limb aimed at, the graduations being indicated by hatched rectangles G. Rectangles C and S, respectively, indicate the slots of the counting and selecting cells. Rectangle R is the slot of the re-setting cell. It will be noted that one graduation G is longer than the other ones, so as to act upon the re-setting cell. The limb may pass along in both directions indicated by arrows F and F. Graduation G ensures or controls the registration of the number transmitted with the limb position. The term resetting means here setting into registration since it is possible to provide several registration marks for various values of the transmitted function. In other words, the function of the re-setting cell is to reset the counting device to zero after a predetermined number of pulses has been counted, this number being simultaneously recorded, and as this is produced under the control of a predetermined graduation mark of the limb, it is evident that in this way the indication recorded registers with the true position of the body about a corresponding axis.

In Fig. 7, are shown four typical positions of a limb graduation with respect to slots C and S of the counting and selecting cells illustrating the manner in which the graduations passing in front of the cells are counted. It will be assumed that the graduations are materialized by opaque or obscure lines on a light background; it would be possible to use as well light lines on a dark background.

Under these conditions, there is shown in Fig. 8 a set of curves in which the full lines show the amplified output signal of the cells, the intensity of said signal being plotted as ordinates and the displacements of the graduation being plotted as abscissae, the marks P P P and P corresponding to the positions of Fig. 7 indicated by the same references. The corresponding displacement directions are indicated by arrows F, F.

Curve c corresponds to the output signal of cell C, curve c shows the pulses obtained after said signal has been transformed into square pulses in a slave multivibrator (not shown), and after said square pulses have been differentiated, and curve s shows the output signal of cell 5 and the corresponding square pulses.

It may be seen that there is an abscissae shift between the output signals of cells C and S, said shift being essential to the use of the method according to the invention. The square signals derived from the output of the cells under the action of a slave multivibrator, as indicated above, are shown in point line for direction F and in dashed line for direction F. Both types of square pulses are slightly shifted along the X axis, due to the phase diiference between the triggering voltages of the electric circuits according as whether said triggering takes place for an increasing signal or for a decreasing one.

The square pulses of cell C are then transformed into sharp positive pulses or pips corresponding to the increasing variation of the output signal of the cell and into {signal of cell, it sufiices .to keep ing device 25 fier 27.

5 negative pulses cor'respoiiding .to the decreasing variation of saidisignals.v The polarity of-the pulses is thus changed when the direction F is turnedoverxto direction .F'. is usedfoncounting; since the pulse polarity is determined by the sign of the variations ofa given edge of .theoutput 'for counting the pulses corresponding either to. the leading edges of the output signal or to its trailing edge. Thus, for example, all

pulses will be ,positive for direction F .and allgwill. be

negative, for direction F or vice versa, which permits .to contend integrate said/pulses inthe counting device specially; provided for this purpose. The function of'the selecting cell S is precisely to transmit only pulses derived from homologous ,edges. This filtering operation, ac-

cording-to the amplitude ofthe voltage of signal S is' effected in a suitable selector. I

For example, only pulses C pertaining to position period lf' -Rzofiliigg. 7'will be transmitted while those occurring during period -P P will bestopped and this, whichever may be the displacement direction,due to the fact that thegpulses of period .P P meet the output of cell S .at a higher amplitude level.

Fig. 9 shows diagrammatically the utilisation circuit of the cell output signals. ,,Rectangle 17 indicates the feeding and amplifying device, of the cell output signals. At the output of device 17,; the Csignal is fed to a slavemultivibrator 18, the gsgsignal is fed to a slave multivibrator 19 and the R signal, which .is the outputsignal generated by the resetting cell .11 ,(Fig. 3) in, response to illumination of the said cell through slotR, is fed to a slave multivibrator 20. The square output pulses from multivibrators .18, .19 and;.20 are-fed to a diflerentiator 21, a selector ,22 and a differentiator23, respectively. The positive pulses from selectorfllare amplified by an amplifier 24 and fed to a tinting device 25 for the adding operations and the peg'ative.pulses;.from selector 22, after having been amplifiedlin an amplifier 26, are fed to said countingdevice .25.for the subtracting operations. On the other hand, the alternatively positive and negative pulses from difierenti'ator 23of the re-setting square signal are fed to countafter a suitable amplification in an ampli- Fig. 5 shows diagrammatically and as an illustration n60" prism28 which may be used as a double separating slot," The light beam projecting the limb graduations is divided at the apex'29 of said pn'sm into two beams which impinge'ithe first one on the counting photo-electric cell Cf'and, the otherone, on theselecting photo-electric cell v Only the useful end of prism .28 is outside, the remainingsurfaces of the prism being; protected by masks 30-301 Masks 30 are separated from the corresponding faces of the prism by very air films. The device operates asfollowsz- 7 ,Any angular displacements of the reference solid S around the fixed point .0 causes a -relative'displacement between one or more of the, three microscopes and the corresponding graduated limb or limbs.

Since the operation is thesame with respect to the three angular displacement axes, it will be sufiicient to describe only one of them. The light rays generated by source 14 impinge upon the graduation of limb 12 which I is at this moment in front of the corresponding microscope axis and' are either reflected or transmitted by transparency, through the optical system of said microscope towards theseparating prism 28 which distributes them between the counting and selecting cells C and S. I Under the action of saidlight rays, said cells generate electric signals" the amplitude of which varies. as 'a function of the light flow impinging upon'the cells, i. e. as a function of theoptical properties of the portions of the limb subjecfted to the impact of the light rays, such as their transparency ortheir reflecting .power, according to Whether said rays are transmitted through said limbs or reflected by .thesa'me.

This

jectedgto the various transformations described .above,

.thus act upon the counting device 25.

Referring to Figs. 9a through 9e, for a more detailed disclosure of the above described arrangement, it will .be noted that rectangles 18, 119 and 20 represent multivibrators having one stable condition or state and. adapted to be triggeredout of said condition by. the input signal whereupon-they reassume by themselves said stable. condition. These rmul'tivibrators are somewhat similar to the so-called flip-flop circuits? well known in the electronic computers.

-Each multivibrator comprises two tubes 42- and 43 '(see Fig. 9a corresponding torectangle 18 and Fig. 9b corresponding to rectangles 19- and 20).

In the case of multivibrator 18, the positive signal from the counting cell C is fed :through amplifier 17 'on the control grid'of tube 42 which was biased to cut-elf in :the absence of the signal. Tube 42'1-iS temporarily made conductive for the duration of the signal, while, due to the coupling between the anode of tube 42 and thelgrid of tube 43, the latter'is temporarily brought to cut-off. v 7

As a result, there is fed simultaneously across the'load resistance of each tube 42'and 43 a square pulse which is negative for tube 42 andp'ositive for tube 43, respectively.

In the case of multivibrator18, both .pulses areinjected into a differentiating-circuit 21.. Inmultivibrators 19 and .20 (see Fig. 9b), which are similarto multivibrator 18, only the positive square pul-sesdrawn across the load resistance of tube 43 are injected into selector .22 from multivibrator, 19 and into .adilferentiating circuit 23 similar to 21 from multivibrator 20, respectively.

I The differentiating circuits 21 and 23'are time constant capacity-resistor circuits.

In 21 (see Fig. 91:), two similar circuits are used .for transforming the input square pulses of. opposite signs intov two opposite and simultaneous sets comprising each two pulses of opposite signs; when the direction .F is reversed into direction F, all pulses. are inverted.

In differentiating circuits 23 (see Fig. 4), One single circuit acts in -the same manner on the positive square pulse signal fed thereto.

The selector 22 (Fig. 9e) comprises two pentodes '44 and 45 mounted inpush-pull. The control grids of both pentodes are fed simultaneously and respectively with the above mentioned opposite sets of two pulsesfrom differentiating circuit 21. The remaining grids are fed, in parallel with the positive rectangular "signal, directly from multivibrator 19.-

In the absence of any signal from 19, tubes '44 and 45 remain in the cut-off condition whatever maybe the lamp 44 corresponding, for example, to direction F, while I lamp 45 corresponds to direction F.

Two pre-amplifier tubes 46 and 47 are fed with the negative pulses from tubes 44 and 45 respectively and generate, across their load resistances, amplified positive pulses. The latter .are fed'through windings of two pulse transformers 48 and 49, one of which isreversely coupled, so that amplifier .24 is fed with positive pulses while amplifier 26 receives negative pulses, the output pulses of both amplifiers being thence injected into counting device 25, .as explained. 1 Y

remaining incut-oif condition since i Whenever it is required to reset the indication of the counting device into registration with the limb position, e. g. after the main feeding circuit has been interrupted, the longer graduation G of the limb provided for this purpose, acts as described above upon the re-setting cell which acts in turn through the various electric devices indicated above, on the counting device.

The second embodiment of the invention is shown in Figs. 10 to 14. In this embodiment, the graduation of the limbs is materialized in the following manner.

The graduation lines to be counted are represented by parts having a high magnetic permeability, separated from one another by low permeability parts which represent the gaps (the converse convention might be clearly adopted).

This arrangement may be embodied in several manners, e. g. it is possible to stack alternatively strips of a high permeability metal (such as anhyster) and strips of a non-magnetic material (such as paper) (Fig. 10a).

It is also possible to provide a flat plate 30 made of a magnetic and homogeneous material in which are engraved graduation lines (Fig. 10b), the thick portions 32 representing said lines and the thin portions 33 representing the gaps therebetween.

There may be also provided a thin brass plate on which is deposited, e. g. divided iron, the graduation lines being then so engraved that the divided iron is completely removed in the bottom of the engravings (Fig. 100).

The reading head represented in Figs. 11 or 12 is constituted by a coil 34 wound on a core of a high magnetic permeability metal 35. Said core has such a "shape that the magnetic circuit is completed through a very narrow gap so that the passage of a line of the graduation in the neighbourhood of said gap varies considerably the reluctance of the magnetic circuit and, thence, the inductance of the coil.

This reading head may be embodied in several manners. For example, the magnetic core may be constituted by a stack of a few metal sheets as indicated at 35 in Fig. 12, the end of each pole shoe having a thickness smaller than or equal to that of a graduation line. Said sheets have the shape of a C or of a rectangle portion interrupted by a gap. The graduation then passes along in the gap.

The reading head may also assume the shape shown in Fig. 11. Thewidth of the gap is then substantially equal to that of a graduation line and said graduation passes along near the gap (at a distance smaller then the width of a line).

When a graduation line of high permeability passes in front of the gap, the reluctance is reduced and, therefore, the inductance of the coil is increased.

1 For measuring this inductance variation, the same may be for example fed to a Wheatstone bridge 36 shown in Fig. 14.

Let n be the maximum number of graduation lines capable of passing in front of the reading head in one second; bridge 36 will then be fed by a source of alternating current having a frequency far higher than n, e. g. equal to lOn, said source being diagrammatically shown at 37. I

When no high permeability graduation line is in front of the reading head, the bridge has no output.

When, however, a graduation line is then in front of said head, an alternating current having a frequency of lOn is obtained at the output of the bridge.

When the graduation passes along in front of the reading head, there is obtained at the output of the bridge an alternating current of frequency 10n modulated at a frequency equal to the number of lines passing in one second in front of the reading head.

After having been suitably amplified in amplifier 38, the current having the lOn frequency is rectified in a rectifier 39 and then fed to a low-pass filter 40, the cut-off frequency of which. is equal to n. Then, there is obtained at the output terminals. 4141 of *said low-pass filter 40 a signal which is a maximum whena line passes in front of the reading head and a minimum in the opposite case. The amplitude of said signal is independent of the speed with which the lines of the graduation pass along in front of the head.

Fig. 13 is a set of curves showing at a the output of the bridge, at b that of the rectifier and at c that of the filter.

In this embodiment of the invention, there is provided as in the optical embodiment described above, three reading heads, the first one ensuring the counting, the second ensuring the selection and the third, being a re-setting head. 1

The output signals of the filter are used in a manner similar to that of the output signals of the photo-electric cells and act, also in a similar manner, upon the counting device.

It is to be understood that the invention is in no way limited to the embodiments described and shown and that many modifications may be made within the scope of the invention. In particular, the reading devices may be fixed, the graduated limbs being movable, but the reverse arrangement may be contemplated as well.

What is claimed is:

l. A device for directly reading and instantaneously recording displacements of a body about a fixed point, comprising three circular reflecting limbs carrying graduations constituted by lines having a colour intensity differing from that of the limbs and spaced according to a. well-defined function of the angular displacements to be meansured, one of said lines being longer than the other ones, each limb being located in one reference plane and having said point for its centre, light sources, microscopes to transmit light rays from said sources reflected on said graduations, optical means to separate the light rays received from each of said microscopes into a pair of beams, a counting photo-electric cell responsive to the variations of intensity of one of each pair of said beams due to said differences of colour intensity to generate electric pulses, a selecting photoelectric cell responsive to the variations of intensity of the other beam of each pair to select among said electric pulses those which correspond to the graduation lines contained in the displacement to be measured, a re-setting photo-electric cell responsive to said longer graduation line of each pair to reset the information transmitted into registration with the position of the limb, recording means to count said last mentioned pulses and to give at any' moment the angular position of said body in the reference system comprising said reference plane and means to transmit said pulses from said electric pulse generating means to said recording means.

2. A device according to claim 1 in which said limbs are dark, while said lines are light.

3. A device according to claim 1 in which said limbs are light, while said lines are dark.

4. A device for instantaneously reading and recording the successive values of three parameters defining the successive instantaneous positions of a body movable about a fixed point, without exerting any perturbative action upon the motion of said body, comprising in combination, three circular graduated limbs, having said point for their common center and adapted to rotate about three mutually perpendicular axes X, Y, Z, respectively at right angles to their planes, said axes all passing through said point, means for generating electric pulses adapted to define said values and means responsive to electric pulses to record said successive values, said pulse generating means comprising, cooperating with each limb, optical reading means for reading the graduations of said limb, a source of light illuminating the graduations of said limb so as to produce two different levels of light output intensity according to whether a graduation is or is not in front of said optical reading means, a pair of photoelectric cells for controlling the generation of said electric pulses, means for directing the light output from said optical means on said two photo-electric cells compris- I ing two adjacent light transmitting passages dividing said light output into two portions directed onto said two cells respectively, said light transmitting passages being of a rectangular cross section, smaller in width than the half width of a single limb graduation and spaced apart so that the distance between their outside edges, equals at maximum the width of such single graduation, so that depending upon the direction of relative movement beof said relative movement.

5. A device for instantaneously reading and recording the successive values of three parameters defining the successive instantaneous positions of a body movable about a fixed point, without exerting any'perturbative action upon the motion of said body, comprising in combination, three circular graduated limbs, having said point for their common center and adapted to rotate about three mutually perpendicular axes X, Y, Z, respectively at right angles to their planes, said axes all passing through said' point, means for generating electric pulses adapted to define said values and means responsive to electric pulses to record said successive values, said pulse generating means comprising, cooperating with each limb, optical reading means for reading graduations of said limb, a source of'light illuminating the graduations of said limb so as to produce two difierent levels of light output intensity according to whether a graduation is or is not in front of said optical reading means, a pair of photoelectric cells for controlling the generation of said electric pulses, means for directing the light output from said optical means on said two photo-electric cells comprising two adjacent light transmitting passages dividing said light output into two portions directed onto said two cells respectively, said light transmitting passages being 10 of a rectangular cross section, smaller in width than the half width of a single limb graduation and spaced apart so that the distance between their outside edges, equals at maximum the width of such single graduation, so that-depending upon the direction of relative movement between the limb and said optical reading means, the electric pulses produced by one of the photo-electric cells upon the passage of a graduation lead or lag with respect to the pulses produced by the other cell, upon the passage at the same graduation, means for mixing the pulses produced by said two cells whereby pulses of one polarity are retained for one direction of relative movement and pulses of opposite polarity are retained for the opposite direction of said movement, whereby they can be additively or subtractively counted depending on the tion of said relative movement.

References Cited in the file'of this patent UNITED STATES PATENTS 464,261 Beehler Dec. 1, 1891 703,139 Lawless June 24, 1902 865,278 Stannard Sept. '3, 1907 1,998,132 Geffcken et a1. Apr. 16, 1935 2,073,246 Merrick- Mar. 9, 1937 2,077,398 Clark Apr. 20, 1937 2,080,490 Kollsman Mayl8, 1937 2,183,765 Coleman Dec. 19, 1939 2,295,000 Morse Sept. 8, 1942 2,339,508 Newell Jan. 18, 1944 2,351,955 Graf Jan. 18, 1944 2,406,299 Koulicovitch Aug. 20, 1946 2,444,933 Jasperson July 13, 1948 2,462,292 Snyder Feb. 22, 1949 2,466,225 Gee Apr. 5, 1949 2,479,802 Young Aug. 23, 1949 2,481,347 Riggin Sept. 6,:1949

FOREIGN PATENTS 186,574 Germany June 26, 1907 192,356 Germany Nov. 9, 1907 22,077 Denmark Apr. 12, 1917 147,690 Great Britain Sept. 15, 1921 75,127 Sweden Aug.23, 1932 direc-

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